Did an open water test across the street with my flat bottom model with the reverse flow sail design. I took model out on a paddle board away from shore on the outside. I used four, 2oz sinkers placed on windward hull of cock pit area. Wind was 8 to 14 with stronger puffs with a true 1 - 1.5 foot chop. Totally amazed at how well it stayed connected to water both hulls showed hardly any slamming from either hull. Just following waters surface and clean slicing through wave tops. It was alittle wet on windward hull side, model was at correct waterline depth/draft for weight. Pretty big stuff and tightly packed too for the models weight, beam, and length. Steering was a little slack needs to be tightened up for free sailing. I was dieing to know how the hulls would ride in the rough stuff. Sorry no video water proof camera had dead batteries. I wish I had some extra batteries though some really good visuals to study. To many things for me to mention but one thing I caught a glimpse of now and then on a big piece of chop, boat getting a beam due to steering issues form slack steering the rise and fall of beam fitting on the single wave. No capsize no windward hull clearing water, but close. Over all vary inspiring.
Todd
--- In harryproa@yahoogroups.com.au, "tsstproa" <bitme1234@...> wrote:
>
>
> Sure 25 knots or there abouts. To get over that constraint, reduce beam width which will lower hull in water for same displacement and drop rocker to raise Cp back up this automatically pushing buoyancy foward to aid in countering bow down trim. Getting us back into a light weight slippery displacment hull with minimum drag.
>
> Todd
>
> --- In harryproa@yahoogroups.com.au, Rick Willoughby <rickwill@> wrote:
> >
> > You need to specify the target speed as well, but assuming 25kts, the
> > lowest drag hull will be very short and designed to plane. The drag
> > for an optimised planing hull at a guess will be around 800N.
> >
> > Constraining the length to > 12m produces a hull requiring 990N to do
> > 25kts. The hull has a lot of rocker and will generate wave making
> > lift as well as significant planing force if flat bottomed with rocker.
> >
> > This is really getting into planing regime rather than displacement
> > and analysis without account for the dynamic lift would not be
> > realistic for 500kg at 25kts on a flat bottom.
> >
> > Dropping the design speed to 14kts for a 500kg hull gives the lowest
> > drag hull of 11m. Drag at 14kts is 380N. Interestingly drag at
> > 25kts is 987N so about the same as the 12m.
> >
> > It takes a lot more effort to actually analyse the trim but I would
> > be surprised if you could not get it to maintain level trim while in
> > displacement mode up to 14kts. After that the planing forces come
> > into play and if it has some rocker the nose lift should overpower
> > the sail moment in the same way you see with a sailing dinghy when on
> > the plane.
> >
> > So the 500kg hull to go fast creates an interesting dilemma. Do you
> > want to go reasonably short and aim to plane or do you want to keep
> > long and slender to achieve wave piercing. It also brings to question
> > what the best shape of an unloaded ww hull might look like at a
> > particular design speed.
> >
> > Rick
> >
> > On 16/07/2010, at 1:25 PM, tsstproa wrote:
> >
> > > What if the same 12m. hull was only 1/2 tonne displacement?
> > >
> > > Todd
> > >
> > > --- In harryproa@yahoogroups.com.au, Rick Willoughby <rickwill@>
> > > wrote:
> > > >
> > > > The length constraint or non-constraint is a function of design
> > > speed
> > > > and weight.
> > > >
> > > > As an example a 1 tonne hull with a flat bottom designed for minimum
> > > > drag at 25 knots results in a length of 12m. However this hull will
> > > > not generate enough bow up moment through wave making to counter the
> > > > moment from the rig to drive it at that speed. Extending the length
> > > > to 15m will get close.
> > > >
> > >
> > >
> >
> > Rick Willoughby
> > rickwill@
> > 03 9796 2415
> > 0419 104 821
> >
>